by Michael, Andreia and George Stiffler
Temperate-growing carnivorous plants (including all North American carnivorous plants) require a cool winter dormancy period. Carnivorous plants that grow in climates with cold winters and shortened daylight periods stop actively growing during this time. In the spring, as weather warms up and the daylight period lengthens, the plants resume growth. Improper handling of dormancy is a common reason for failure with temperate-growing carnivorous plants. In general, the dormancy period should last three to four months. Watering should be decreased during this time, keeping the medium damp only. The plants should experience a decreased photoperiod; light intensity is not important as long as additional unwanted heat is not produced. Most importantly, the plants should experience a decrease in temperature. Temperatures above freezing to 45ºF are ideal, although most plants will survive brief periods of freezing.
Here we outline our techniques for indoor dormancy, and provide some advice for situations that are not exactly the same as ours.
Generally, this method involves first uprooting plants and carefully clipping all leaves. Dust plants lightly with a fungicide. Then, place plants individually or in small groups in plastic bags, including some moist long-fibered sphagnum moss. Then simply place plants in the refrigerator. Check plants periodically for dryness or fungus.
Alternatively plants can be left in their pots and covered with plastic bags. Or, if room permits, leave the plants in their pots and place them in a small terrarium with a cover and lightstrip, leave the lights on for 8-10 hours per day. It’s not entirely necessary to clip leaves, but clipping leaves does provide less substrate for fungus growth. The refrigerator method typically works well, but frequent losses can occur with smaller plants usually due to fungus attacks. This method is recommended if no other option is open.
This method requires access to a garage, one that is attached to the house. Using an unattached garage may also work, use of a heater to prevent freezing of the plants would be required though. Simply place plants in their pots in a convenient location in the garage. It’s best if the plants receive some light from a window, otherwise one could use a standard shoplight fixture held a few feet above the plants and set on an 8-hour photoperiod. Water plants very lightly. If the outdoor temperature is expected to fall much below freezing, bring the plants inside for a few days and place them in a cool basement.
This method is preferred over the refrigerator method, the main reason being that fungus is less of a problem due to the air circulation. Also, the plants get to experience a more natural dormancy-wake cycle with gradual changes in temperature and light duration.
References and for more information
1. D’Amato, Peter. 1998. The Savage Garden. Berkeley, California: Ten Speed Press.
2. The Carnivorous Plant FAQ